His corner told him he won. He says, "I'm sure I won." which is exactly what people say when they are not sure!
It's like... I'm sure I locked the door. I'm sure I left my car here. I'm sure I did have a condom on. That kind of thing.
To me, it seems like he is looking for assurances that he won, but he wasn't sure himself. I think both fighters we're equally unsure at the end of the fight. I bet neither really want to go through that again but they'll say, "Sure, I would like a rematch."... and then go home and cry.